The present invention relates to a VoIP (Voice over Internet Protocol) gateway apparatus and, in particular, to a technology for diverting a call received from an accommodated device from an IP network to a detour network and a technology for relaying a call received from a detour network to an accommodated device.
Japanese Patent Laid-Open Publication No. 2000-312229 (hereinafter, referred to as Patent Document 1) discloses a technology for allowing the continuation of voice communication even when the quality of communication over the Internet is lowered. In Patent Document 1, a voice gateway apparatus includes an interface for controlling a call connection to a PSTN (Public Switched Telephone Network). When low quality in communication over the Internet is detected in this case, a call is connected to the other party over the PSTN, and voice communication with the other party is switched from voice communication over the Internet to voice communication over the PSTN.
Japanese Patent Laid-open Publication No. 2001-36641 (hereinafter, referred to as Patent Document 2) discloses a technology for connecting a call between telephone terminals over the Internet or a PSTN. In Patent Document 2, an exchange at the time of calling accesses a database which stores subscriber information such as the presence of subscriptions to an Internet Protocol telephone service by the caller and the receiver and the type or types of the telephone terminals, determines either the Internet or a PSTN is to be used for the connection based on the subscriber information obtained from the database based on the called party number dialed by the caller and subscriber information of the caller and implements call connection over the determined route.